1. Field of the Invention
This invention relates to a device for converting X-ray energy into resistance to the passage of a steady electric current and a method for utilizing such resistance to align an X-ray diffraction camera. More specifically this invention comprises a device which is adapted for use with an X-ray diffraction camera wherein a fluorescent material is disposed in said device in a position where X-rays entering said camera contact said fluorescent material, excite fluorescence therein which in turn excites a conductive photo-cell disposed adjacent to said fluorescent material wherein the resistance of said photo-cell to the passage of a steady electric current is altered and utilized to indicate the position of said camera, with respect to said X-rays, whereat the maximum intensity of said X-rays will contact a substance placed within said camera for X-ray diffraction analysis.
2. Prior Art
X-ray diffraction analysis of crystalline substances has been a recognized analytical tool for a long time. Such an analysis is highly useful for determining the degree or percentage of crystallinity of a substance or for measuring the sameness of the crystals in a sample which may be composed of more than one substance.
An X-ray diffraction camera is generally designed as a rather wide but shallow cylinder. The cylinder has two oppositely positioned ports in the sides thereof. A means is provided in the longitudinal center of the cylinder to place a small sample in a position that is both vertically and horizontally aligned with the two aforementioned ports. A means is provided to rotate said sample. The cylinder is closed on both ends, but the closure on one end is in the form of a door which can be opened and closed to position the sample and an unexposed photographic film in said cylinder. The photographic film is disposed around the interior perimeter of the cylinder.
In operation, the X-ray diffraction camera is positioned adjacent to a source of X-ray emission so that said X-rays can enter through one of the ports described above. The X-rays bombard the sample which is slowly rotated and are diffracted at an angle which is characteristic for the crystals being bombarded, and the X-rays contact the unexposed photographic film and cause an exposure of such film where the contact is made. Exposed film is compared with a standard film exposed from the bombardment of known crystals and an analysis can be computed therefrom.
In order to make full use of the precision and reliability of X-ray diffraction analysis it is important to maximize the intensity of the bombardment of each sample with direct (as contrasted with deflected) X-rays. The closer each sample comes to a uniform intensity, the greater the reliability and preciseness of the comparison of the X-ray diffraction pattern with a known standard.
In the past the X-ray diffraction camera has been aligned for maximum intensity of the X-rays contacting the sample by placing, in the port in the cylinder opposite the port through which the X-rays enter the camera, a device therein which comprises an elongated housing in which there is laterally disposed a fluorescent substance. Behind such fluorescent substance there is a piece of leaded glass through which the fluorescence of such substance can be observed. The room has been darkened, the X-ray generation begun and the camera manually manipulated to a position wherein the fluorescence has appeared to the eye to be the brightest. In practice it was found by consecutive analyses of identical samples that the adjustment of the intensity of the X-ray bombardment could vary as much as 60 percent when the same operator observed the brightness of the fluorescence. The result has been a loss in precision and reliability of the X-ray diffraction analyses.
Accordingly, it is an object of this invention to provide a device for quantitatively measuring the intensity of the direct X-rays to which a sample of material undergoing X-ray diffraction analysis is exposed in a diffraction camera, said device differentiating the relative intensity of such X-rays.
Another object of this invention is to provide a device which will convert X-ray energy to resistance to the passage of a steady electric current in a linear relationship in which the quantum of such resistance is inversely dependent upon the intensity of the X-rays entering the device.
Still another object of this invention is to provide a method for adjusting an X-ray diffraction camera in which the useful device described herein is utilized to maximize the intensity of the X-ray bombardment of a sample of material undergoing X-ray diffraction analysis in said camera.